You will need the Full Write Financial permission to perform this action for other people. You can always delete your own recurring schedules.
Navigate to the person's profile and click on the "Giving" tab. Then select the "Schedules" sub tab. The action (delete or deactivate) available depends on whether the schedule has already processed a transaction.
Delete - the schedule has not run yet so you can completely remove it from the system.
Deactivate - the schedule has run at least once. You can no longer delete it, but you can deactivate it so that it will no longer charge.
You can also delete/deactivate a schedule by locating it within the main listing.